JP7554164B2 - Linear object installation method - Google Patents

Description

The present invention relates to a method for installing a linear body in the ground.

When constructing a tunnel or underground cavity, a linear object is sometimes installed in the ground and used to detect the condition of the ground. Patent Document 1 discloses a method of installing an optical fiber cable in the ground as a linear object for measuring ground displacement.

In the method disclosed in Patent Document 1, positioning spacers are provided along the circumferential and axial directions on the outer surface of the pipe to which the optical fiber cable is attached so that the optical fiber cable inserted into a borehole formed in the ground is positioned at a predetermined position.

JP 2002-156215 A

In the method disclosed in Patent Document 1, positioning spacers are provided over the range in which the optical fiber cable is to be installed. Therefore, the longer the borehole, the more positioning spacers must be attached to the pipe, and in order to position the optical fiber cable in the specified position, the positioning spacers must be attached as evenly as possible in the circumferential and axial directions. This increases the amount of preparation work required before inserting the optical fiber cable into the borehole, which may result in a longer construction period.

The present invention aims to efficiently position a linear body to be installed in the ground.

The present invention is a linear body installation method for installing a linear body in a hole formed in the ground, the method including the steps of: inserting into the hole a hollow pipe material having a tip end provided with an expandable body that can be expanded radially outward of the hole and having the linear body attached along the axial direction to its outer peripheral surface; a tip end fixing step expanding the expandable body radially outward to fix the tip end of the pipe material to the hole; a base end fixing step fixing the base end of the pipe material to the hole at an open end of the hole ; and a filling step filling the hole with a filling material through a filling hose, the pipe material having a communication hole connecting the inside and outside, the discharge port of the filling hose being positioned vertically below the communication hole, and in the filling step, the filling material is filled between the outer peripheral surface of the pipe material and the inner wall surface of the hole from the open end side, thereby discharging air in the hole through the communication hole to the outside.
The present invention also relates to a linear body installation method for installing a linear body in a hole formed in the ground, the method including: an insertion step of inserting a rod material, the tip of which is provided with an expandable body that can be expanded radially outward of the hole, and the linear body attached to its outer peripheral surface along the axial direction, into the hole; a tip fixing step of expanding the expandable body radially outward to fix the tip of the rod material to the hole; a base end fixing step of fixing the base end of the rod material to the hole at an open end of the hole; and a filling step of filling the hole with filling material through a filling hose, wherein an exhaust pipe for discharging air in the hole to the outside in the filling step is provided along the rod material, and an outlet of the filling hose is positioned vertically below the open end of the exhaust pipe, and in the filling step, the filling material is filled between the outer peripheral surface of the rod material and the inner wall surface of the hole from the open end side, thereby discharging the air in the hole to the outside through the exhaust pipe.
The present invention also relates to a linear body installation method for installing a linear body in a hole formed in the ground, the method including: an insertion step of inserting into the hole a hollow pipe material having a tip end provided with an expandable body that can be expanded radially outward of the hole and having the linear body attached along the axial direction to its outer peripheral surface; a tip fixing step of expanding the expandable body radially outward to fix the tip end of the pipe material to the hole; a base end fixing step of fixing the base end of the pipe material to the hole at an opening end of the hole; and a filling step of filling the hole with filling material through a filling hose, wherein in the filling step, an exhaust pipe for discharging air in the hole to the outside is provided along the pipe material, and an outlet of the filling hose is positioned vertically below the opening end of the exhaust pipe, and in the filling step, the filling material is filled between the outer peripheral surface of the pipe material and the inner wall surface of the hole from the opening end side, thereby discharging the air in the hole to the outside through the exhaust pipe.

According to the present invention, it is possible to efficiently position a linear body to be installed in the ground.

1 is a diagram showing a linear object installed in a hole by a linear object installation method according to an embodiment of the present invention. FIG. 1A to 1C are diagrams showing a linear object installation method according to an embodiment of the present invention in chronological order. 3A to 3C are diagrams showing a linear object installation method according to an embodiment of the present invention in chronological order, following FIG. 2 . 13A to 13C are diagrams illustrating a modified example of the linear object installation method according to the embodiment of the present invention.

Below, a linear object installation method according to an embodiment of the present invention will be described with reference to the drawings.

First, referring to Figures 1 to 3, the process and configuration for installing a linear object in a hole formed in the ground using a linear object installation method according to an embodiment of the present invention will be described. Here, the case where the linear object is an optical fiber cable will be described. Note that, in addition to optical fiber cables, examples of the linear object include electric wires, which are linear members capable of measuring temperature, strain, etc. with high accuracy.

When constructing civil engineering structures, it is important to understand the condition of the ground, such as landslides. Also, understanding the progress of loose areas in the ground that occur during the excavation of underground cavities such as tunnels is important in order to proceed with the excavation in a stable state. Therefore, optical fiber cables are sometimes installed in boreholes excavated in the ground to detect distortions and loose areas in the ground.

Since optical fiber cables buried in a borehole are distorted in response to strain in the ground and loosening of the ground, it is possible to measure strain in the ground and loosening of the ground by measuring the strain in the optical fiber cable.

Specifically, optical fiber cables have the property of slightly scattering incident pulsed light backwards, and by utilizing this property, it is possible to measure the strain at multiple positions in the optical fiber cable. Because the frequency of the scattered light depends on the strain in the optical fiber cable, it is possible to measure the strain in the optical fiber cable by injecting pulsed light into the optical fiber cable and measuring the frequency of the scattered light. In addition, by measuring the time it takes for the scattered light generated within the optical fiber cable to return to the incident position after pulsed light is injected into the optical fiber cable, it is possible to measure the position where the scattered light occurred, i.e., the position where the strain occurred in the optical fiber cable.

Therefore, by burying an optical fiber cable in a borehole excavated in the ground and measuring the strain of the buried optical fiber cable, it is possible to measure the strain in the ground and loosening of the ground that occurs at multiple locations, and as a result, the condition of the ground can be accurately grasped.

When excavating an underground cavity such as a tunnel, it is necessary to understand the condition of the ground above and to the sides of the underground cavity. In this case, the borehole into which the optical fiber cable is inserted is formed so that it faces upwards more vertically or horizontally. In other words, the optical fiber cable needs to be inserted vertically or horizontally and then buried in the borehole.

However, optical fiber cables are generally flexible and difficult to stand on their own, so it is virtually impossible to insert an optical fiber cable alone over a relatively long distance of 10 m or more into a borehole formed vertically upward or higher than the horizontal direction.

In addition, to integrate the optical fiber cable with the ground, the borehole into which the optical fiber cable is inserted is filled with grout such as cement bentonite, but this requires filling the grout against gravity in boreholes that are formed vertically upward or higher than horizontally.

Furthermore, even if it is possible to fill the borehole with grout into which the optical fiber cable has been inserted, if the optical fiber cable is buried in a meandering state within the borehole, there will be places where there is almost no gap between the inner wall of the borehole and the optical fiber cable, or places where the gap is too large. If the gap between the inner wall of the borehole and the optical fiber cable varies in this way, the strain transmitted from the ground to the optical fiber cable will also vary, and as a result, there is a risk that the condition of the ground will not be accurately grasped using the optical fiber cable.

In order to solve such problems, in the linear body installation method according to the present embodiment, as shown in Figs. 1 to 3, a rod 10 and an optical fiber cable 50 (linear body) are inserted into a borehole 2 (hole) drilled in the ground 1, and then the tip and base ends of the rod 10 are fixed to the borehole 2, thereby efficiently positioning the optical fiber cable 50 in the borehole 2, and the distance between the inner wall surface of the borehole and the optical fiber cable does not vary in the axial direction, regardless of the direction in which the borehole 2 is drilled. Fig. 1 is a schematic diagram showing the state of the optical fiber cable 50 installed in the borehole 2 by the linear body installation method according to the present embodiment and the holding unit 100 that holds a part of the optical fiber cable 50, and Figs. 2(A) to 2(C) and 3(A) to 3(C) are diagrams showing the linear body installation method according to the present embodiment in chronological order.

First, referring to FIG. 1, an optical fiber cable 50 installed in a borehole 2 by a linear object installation method described in detail below and a holding unit 100 that holds the optical fiber cable 50 will be described. Note that the following description will be given for a case in which the borehole 2 is drilled vertically upward.

The holding unit 100 has a rod 10 (pipe 10) to which an optical fiber cable 50 is attached along the axial direction, an expander 20 attached to the tip of the rod 10 (pipe 10) and capable of expanding radially outward of the borehole 2, and a filling hose 30 provided along the rod 10 (pipe 10). The rod 10 is a long member having an outer diameter sufficiently smaller than the inner diameter of the borehole 2, and is preferably a hollow pipe 10 as shown in FIG. 1.

The pipe material 10 is a hollow tubular member made of resin such as polyvinyl chloride, and has an internal passage 11 formed by penetrating in the axial direction, and a communication hole 12 that opens at one end on the inner peripheral surface of the internal passage 11 and communicates between the inside and outside of the pipe material 10. The communication hole 12 is formed at the tip side of the pipe material 10 when the holding unit 100 is inserted into the borehole 2, and functions as an exhaust port that exhausts air from within the borehole 2 to the outside of the borehole 2 during the filling process described below.

The expansion body 20 has an expansion section 22 that expands radially outward in response to the pressure of the fluid supplied, a support section 21 that supports the expansion section 22 radially inward, and a supply pipe 24 that supplies the pressurized fluid. Figure 1 shows the state in which the expansion section 22 expands radially outward of the borehole 2 and presses against the inner wall surface of the borehole 2. In this expanded state of the expansion section 22, the axis of the expansion section 22 and the axis of the support section 21 are approximately aligned, and they are arranged concentrically.

The expansion section 22 is a rubber or metal member having a barrel-shaped or cylindrical outer shape, and is supported by the support section 21 so as to expand radially outward in response to the pressure of the fluid supplied to the space (not shown) formed between the support section 21 and the expansion section 22.

The fluid supplied to the expansion body 20 is, for example, pressurized water, and the expansion section 22 presses the inner wall surface of the borehole 2 with a load according to the water pressure. Note that the fluid supplied to the expansion body 20 is not limited to water, and may be compressed air or pressurized hydraulic oil.

The support part 21 is a cylindrical member having a through hole 21a formed therethrough in the axial direction, and one axial end is connected to the tip of the pipe material 10 via a connecting member (not shown). When the support part 21 is connected to the pipe material 10, the through hole 21a of the support part 21 and the internal passage 11 of the pipe material 10 are in communication with each other.

On the other hand, as shown in FIG. 1, the other axial end surface 21b of the support portion 21 is pressed against the bottom surface 2a of the borehole 2 when the holding unit 100 is inserted into the borehole 2. In other words, the other axial end surface 21b of the support portion 21 functions as a regulating surface that regulates the length of the holding unit 100 inserted into the borehole 2.

The supply pipe 24 is attached to the pipe material 10 along the axial direction, and one end 24a of the supply pipe 24 opens into the space formed between the support portion 21 and the expansion portion 22. The other end 24b of the supply pipe 24 is connected to a fluid supply source such as a pump (not shown) outside the borehole 2 before the pressurized fluid is supplied to the expansion portion 22 through the supply pipe 24, and is accommodated in the borehole 2 as shown in FIG. 1 when the supply of fluid to the expansion portion 22 is completed. In addition, in order to maintain the expanded state of the expansion portion 22 once it has expanded, a check valve that prevents the supplied fluid from flowing back may be provided on the supply pipe 24.

The filling hose 30 is a hose through which the grout 40 to be filled in the borehole 2 in the filling process described below flows, and the outlet 30a for discharging the grout 40 is attached along the pipe material 10 so as to open in the borehole 2. As shown in FIG. 1, the position of the outlet 30a is set vertically below the communication hole 12 formed in the pipe material 10 when the holding unit 100 is inserted in the borehole 2. Note that the outlet 30a only needs to be located vertically below the communication hole 12, and may be located, for example, near the opening end 2b of the borehole 2. The other end of the filling hose 30 is connected to a grout delivery pump (not shown) outside the borehole 2.

The optical fiber cable 50 held by the holding unit 100 is a linear member with a flat cross-sectional shape in which multiple optical fibers and steel wires (not shown) are covered with a resin material, and the tip 50a of the optical fiber cable 50 is sealed with a sealing material such as oil or silicone to prevent reflections from occurring at the tip surface. By using an optical fiber cable 50 with a flat cross-sectional shape, it is possible to run the optical fiber cable 50 in a straight line along the surface of the pipe material 10 while avoiding twisting of the optical fibers inside.

The tip 50a of the optical fiber cable 50 is inserted into the internal passage 11 of the pipe material 10 and the through hole 21a of the support part 21 through the communication hole 12 formed in the pipe material 10, and is fixed near the other axial end face 21b of the support part 21 with adhesive, silicone, or the like. The borehole 2 is drilled to a predetermined depth, and the other axial end face 21b that abuts against the bottom surface 2a of the borehole 2 is located at the deepest part of the borehole 2. Therefore, by fixing the tip 50a of the optical fiber cable 50 near the other axial end face 21b, the tip 50a can be used as a reference point when measuring the distortion of the ground 1 along the borehole 2.

Meanwhile, the other end of the optical fiber cable 50 is connected to a measuring device 60 outside the borehole 2.

In order to prevent the blocked tip 50a from being scratched or damaged when the optical fiber cable 50 is inserted into the borehole 2, the through hole 21a of the support part 21 may be blocked on the other axial end face 21b side.

In addition, the folded portion of the optical fiber cable 50 may be fixed in the support portion 21 instead of the tip portion 50a of the optical fiber cable 50, and in this case, both ends of the optical fiber cable 50 are connected to the measuring device 60.

The three components, the optical fiber cable 50, the supply pipe 24, and the filling hose 30, which are arranged along the outer circumferential surface of the pipe material 10 in the axial direction, are fixed to the pipe material 10 by fixing tape 14. Multiple fixing tapes 14 are provided at predetermined intervals in the axial direction.

The holding unit 100 further has a flange 16 at the open end 2b of the borehole 2 for fixing the base end of the pipe material 10 to the borehole 2.

The flange 16 is a plate-like member provided to support the base end of the pipe material 10 that protrudes outside the borehole 2 when the holding unit 100 is inserted into the borehole 2, and has an insertion hole 16a through which the pipe material 10 and the optical fiber cable 50 and filling hose 30 provided around the pipe material 10 can be inserted, and a number of bolt holes 16b through which anchor bolts 4 embedded in the ground 1 to surround the opening of the borehole 2 can be inserted.

The flange 16 is fixed to the borehole 2 by tightening the nut 5 screwed onto the anchor bolt 4. The positions of the insertion hole 16a and bolt hole 16b formed in the flange 16 and the position where the anchor bolt 4 is embedded are preset so that the axis of the pipe material 10 inserted into the insertion hole 16a approximately coincides with the axis of the borehole 2.

The insertion hole 16a of the flange 16 has an inner diameter that allows the pipe material 10 and the optical fiber cable 50 and filling hose 30 provided around the pipe material 10 to be inserted with ease. As a result, a gap is created between the inner surface of the insertion hole 16a of the flange 16 and the outer surface of the pipe material 10, the optical fiber cable 50, and the filling hose 30. This gap is sealed with a sealant such as an epoxy adhesive or ultra-fast hardening cement (not shown).

The flange 16 is also provided with a sealant injection hole (not shown) whose one end opens into the borehole 2. In the base end fixing process described below, a sealant 18 such as a urethane material is injected through the sealant injection hole into the borehole 2 near the flange 16, thereby closing off the open end 2b of the borehole 2 and blocking off the space within the borehole 2 from the outside.

The flange 16 does not have to be a single plate-like member, but may be a divided flange made up of multiple members that partially overlap each other to form the insertion hole 16a. Also, instead of forming a sealant injection hole in the flange 16, an injection hose for injecting the sealant 18 may be separately inserted into the insertion hole 16a.

The space in the borehole 2 that has been blocked by injecting the sealing material 18 into the open end 2b is filled with grout 40 (filler) such as cement bentonite through the filling hose 30, so that the optical fiber cable 50 is buried in the borehole 2 together with the pipe material 10 and is substantially integrated with the ground 1. When the grout 40 is filled, the air in the borehole 2 is discharged to the outside of the borehole 2 through the communication hole 12 and internal passage 11 of the pipe material 10.

Next, with reference to Figures 2 and 3, a method for installing an optical fiber cable 50 in a borehole 2 as shown in Figure 1 will be described.

First, an insertion process is performed in which the pipe material 10 to which the optical fiber cable 50 is attached is inserted into the borehole 2.

In this process, as shown in FIG. 2(A), the holding unit 100 having the above configuration is gradually inserted vertically upward into the borehole 2. At this point, the expansion portion 22 of the expansion body 20 is not expanded, and the outer diameter of the expansion body 20 is smaller than the inner diameter of the borehole 2. The insertion process is completed when the other axial end surface 21b of the support portion 21 of the expansion body 20 abuts against the bottom surface 2a of the borehole 2.

Once the insertion process is complete, a tip fixing process is then carried out to fix the tip of the pipe material 10 inserted into the borehole 2 to the borehole 2.

In this process, as shown in FIG. 2(B), the tip portion of the pipe material 10 on which the expansion body 20 is provided is fixed to the borehole 2 by expanding the expansion body 20 radially outward.

Specifically, pressurized water is supplied to the expansion section 22 through the supply pipe 24, causing the expansion section 22 to expand radially outward. The expansion section 22 generates a load that presses against the inner wall surface of the borehole 2, and the tip of the pipe material 10 is fixed to approximately the center of the borehole 2 via the diameter expansion body 20. In other words, the part of the holding unit 100 where the diameter expansion body 20 is provided is in a state where it cannot move radially, while the part of the holding unit 100 located near the opening end 2b of the borehole 2 is still able to move radially.

Once the tip fixing process is completed in this manner, the base end fixing process is then carried out to fix the base end of the pipe material 10 to the borehole 2 at the open end 2b of the borehole 2.

In this process, as shown in FIG. 2(C), the base end of the pipe material 10 that protrudes outside the borehole 2 is fixed to the borehole 2 via a flange 16.

Specifically, first, the pipe material 10 and the optical fiber cable 50 and filling hose 30 provided around the pipe material 10 are inserted into the insertion hole 16a of the flange 16, and the anchor bolt 4 embedded in the ground 1 is inserted into the bolt hole 16b of the flange 16. The supply pipe 24 attached along the pipe material 10 together with the optical fiber cable 50 is cut near the opening end 2b of the borehole 2 when the supply of pressurized water to the expansion section 22 is completed in the tip fixing process, and the other end 24b of the supply pipe 24, which is the cut end, is accommodated in the borehole 2 without being inserted into the insertion hole 16a.

Then, the nut 5 threaded onto the anchor bolt 4 is tightened, thereby fixing the flange 16 to the borehole 2.

By fixing the flange 16 to the borehole 2, the space between the outer peripheral surface of the pipe material 10, into which the filler material is filled in the filling process described below, and the inner peripheral surface of the borehole 2 is almost completely blocked by the flange 16. In other words, the flange 16 functions as a shielding member that prevents the filler material filled in the borehole 2 from leaking out.

In addition, by fixing the flange 16 to the borehole 2, the base end of the pipe material 10 is restricted from moving radially approximately at the center of the borehole 2, i.e., is fixed to the borehole 2.

When the tip and base ends of the pipe material 10 are fixed to the borehole 2 in this manner, the distance between the optical fiber cable 50 attached to the pipe material 10 along the axial direction and the inner wall surface of the borehole 2 becomes approximately the same in the axial direction. In other words, by fixing the tip and base ends of the pipe material 10 to the borehole 2, the positioning of the optical fiber cable 50 relative to the borehole 2 is completed.

In addition, in the base end fixing process, an injection process is also performed to inject a sealant 18 into the open end 2b of the borehole 2 as a preparation process for the filling process to fill the borehole 2 with grout 40. The injection process is performed to prevent the grout 40 filled in the borehole 2 in the filling process described below from leaking out from the open end 2b of the borehole 2.

In the injection process, as shown in FIG. 3(A), a sealant 18 such as a urethane material is injected into the borehole 2 through a sealant injection hole (not shown) provided in the flange 16.

Specifically, first, in order to prevent the sealing material 18 from leaking out of the borehole 2, a sealant such as ultra-fast-setting cement (quick-setting cement) is applied to the gap between the inner circumferential surface of the insertion hole 16a of the flange 16 and the outer circumferential surface of the pipe material 10, the optical fiber cable 50, and the filling hose 30. The sealant may be applied when the pipe material 10 is inserted into the insertion hole 16a, or after the pipe material 10 is inserted into the insertion hole 16a. The sealant may also be applied to the contact surface between the flange 16 and the ground 1.

Once the applied sealant has solidified, the sealant 18 is injected through a sealant injection hole provided in the flange 16. Once the injection of a preset amount of sealant 18 has been completed, the sealant injection hole is sealed with a plug material (not shown).

The sealing material 18 injected into the borehole 2 solidifies so as to close the open end 2b of the borehole 2. This results in the space within the borehole 2 being almost completely sealed off from the outside, meaning that even if the borehole 2 is filled with grout 40, it is possible to prevent the grout 40 from leaking out of the open end 2b of the borehole 2.

Next, when the base end fixing process, including the injection process, is completed and the injected sealing material 18 has solidified, that is, when the sealing material 18 injected into the open end 2b has solidified and the space between the outer surface of the pipe material 10 and the inner surface of the borehole 2 is sealed off from the outside, the filling process is performed to fill the borehole 2 with grout 40.

In this process, as shown in FIG. 3(B), grout 40 is injected as a filler into the borehole 2 through the filling hose 30.

Specifically, grout 40 pumped from a pressure pump (not shown) passes through the filling hose 30 and is discharged from the discharge port 30a into the borehole 2. The grout 40 discharged into the borehole 2 flows downward vertically due to gravity, and the space in the borehole 2 is gradually filled with grout 40 from the open end 2b side.

The open end 2b of the borehole 2 is blocked by the sealing material 18 as described above, so that the grout 40 is prevented from leaking out from the open end 2b of the borehole 2 to the outside.

As described above, the pipe material 10 has a communication hole 12 that connects the inside and outside of the pipe material 10. As the borehole 2 is filled with grout 40, the air in the borehole 2 is discharged to the outside of the borehole 2 through the communication hole 12 and the internal passage 11.

When the borehole 2 is further filled with grout 40, the liquid level of the grout 40 eventually reaches the communication hole 12, as shown in Figure 3 (C).

When the filled grout 40 reaches the communication hole 12, some of the grout 40 leaks out of the borehole 2 through the communication hole 12 and the internal passage 11. When it is confirmed that the grout 40 has leaked out through the pipe material 10, the pressure transfer of the grout 40 through the filling hose 30 is stopped, and the filling process is completed.

As described above, when the tip fixing process and base end fixing process are completed, the positioning of the optical fiber cable 50 relative to the borehole 2 is complete, and the position of the optical fiber cable 50 is maintained even during the filling process. In particular, by fixing both the tip and base ends of the pipe material 10 to the borehole 2, rather than just one of them, the position of the optical fiber cable 50 relative to the borehole 2 is reliably maintained in a predetermined position without being displaced by the pressure of the grout 40.

Therefore, when the grout 40 filled in the filling process solidifies, the optical fiber cable 50 is embedded in the borehole 2 with the distance between the optical fiber cable 50 and the inner wall surface of the borehole 2 being approximately the same size without any variation in the axial direction, as shown in Figure 1.

In this way, the strain in the ground around the borehole 2 in which the optical fiber cable 50 is buried is transmitted from the inner wall surface of the borehole 2 through the solidified grout 40 to the optical fiber cable 50 without any variation. Therefore, by measuring the strain of the optical fiber cable 50 installed in the borehole 2 as described above, the position and magnitude of the strain in the ground can be measured with high accuracy.

The strength and rigidity of the grout 40 interposed between the ground 1 and the optical fiber cable 50 is adjusted to be equal to or smaller than the strength and rigidity of the ground 1, taking into consideration the transmission of strain and other factors underground to the optical fiber cable 50.

The above embodiment provides the following advantages:

According to the linear body installation method of this embodiment, in the tip fixing process, the tip of the pipe material 10 to which the optical fiber cable 50 is attached along the axial direction is fixed to the borehole 2, and in the base end fixing process, the base end of the pipe material 10 is fixed to the borehole 2 at the opening end 2b of the borehole 2.

By fixing the tip and base ends of the pipe material 10 to the borehole 2 in this manner, the distance between the optical fiber cable 50 attached to the pipe material 10 along the axial direction and the inner wall surface of the borehole 2 is approximately the same in the axial direction. In other words, by fixing the tip and base ends of the pipe material 10 to the borehole 2, the position of the optical fiber cable 50 relative to the borehole 2 is reliably maintained at a predetermined position.

Therefore, the above-mentioned linear body installation method makes it possible to efficiently position the optical fiber cable 50 within the borehole 2.

The optical fiber cable 50 is buried in the borehole 2 with the distance between the optical fiber cable 50 and the inner wall surface of the borehole 2 being approximately the same in the axial direction, so that the strain in the ground around the borehole 2 is transmitted from the inner wall surface of the borehole 2 through the solidified grout 40 to the optical fiber cable 50 without any variation. Therefore, by measuring the strain of the optical fiber cable 50 installed in the borehole 2, the position and magnitude of the strain in the ground can be measured with high accuracy.

The following modified examples are also within the scope of the present invention, and it is possible to combine the configurations shown in the modified examples with the configurations described in the above embodiments, or to combine the configurations described in the different modified examples below.

In the above embodiment, the supply pipe 24 and the filling hose 30 are provided along the axial direction on the outer circumferential surface of the pipe material 10 together with the optical fiber cable 50. Alternatively, the supply pipe 24 and the filling hose 30 may be provided through the internal passage 11 of the pipe material 10, as in the modified example shown in FIG. 4.

Specifically, one end of the supply pipe 24, which is connected to the space between the support section 21 and the expansion section 22, is pulled out to the outside of the pipe material 10 through the communication hole 12, and the discharge port 30a of the filling hose 30 is pulled out to the outside of the pipe material 10 through the communication hole 12. The discharge port 30a is fixed to the pipe material 10 by the fixing tape 14 so that it is located vertically below the communication hole 12.

In this modified example, only the pipe material 10 and the optical fiber cable 50 are inserted into the insertion hole 16a of the flange 16, so the gap between the inner surface of the insertion hole 16a and the pipe material 10, etc. can be easily sealed with a sealant.

In the above embodiment, a hollow pipe material 10 is used as the rod material 10 to which the optical fiber cable 50 is attached. Alternatively, the rod material 10 may be a solid rod-shaped member. In this case, an exhaust pipe for exhausting the air in the borehole 2 to the outside during the filling process is separately provided along the rod material 10.

In the above embodiment, the expandable body 20 expands radially outward in response to the pressure of the fluid being supplied. Alternatively, the expandable body 20 may be of any type as long as it has a configuration that allows it to be expanded when insertion into the borehole 2 is complete. For example, it may be mechanically expanded by contacting the bottom surface 2a of the borehole 2, or may be equipped with a gas generator that generates gas to expand the expansion section 22 in response to contact with the bottom surface 2a or switch operation.

In the above embodiment, the linear body is an optical fiber cable 50, but the linear body installed in the borehole 2 is not limited to this, and may be any linear body capable of detecting the state of the ground 1, for example, a linear body in which multiple sensors capable of detecting pressure or temperature are connected at equal intervals, or a metal wire such as a thermocouple. The state of the ground 1 to be detected is not limited to distortion in the ground, and may be the temperature or pressure in the ground.

In the above embodiment, the borehole 2 is drilled vertically upward, but the borehole 2 may be drilled vertically downward, or may be drilled horizontally or upward or downward at a predetermined angle from the horizontal. Even when the borehole 2 is drilled in this manner, the optical fiber cable 50 can be efficiently positioned within the borehole 2 by the above-mentioned method.

Although the embodiments of the present invention have been described above, the above embodiments merely show some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

1... Ground 2... Borehole (hole)
2a: bottom surface 2b: open end 10: rod material (pipe material)
11: Internal passage 12: Communication hole 16: Flange 18: Sealing material 20: Expansion body 30: Filling hose 40: Grout (filling material)
50...Optical fiber cable (linear body)
60: Measuring device 100: Holding unit

Claims (4)

A linear object installation method for installing a linear object in a hole formed in ground, comprising the steps of:
an insertion step of inserting a hollow pipe material into the hole, the hollow pipe material having a distal end portion provided with a diameter expandable body radially outward of the hole and the linear body attached to an outer peripheral surface of the hollow pipe material along an axial direction;
a tip portion fixing step of fixing the tip portion of the pipe material to the hole by expanding the diameter expansion body radially outward;
a base end fixing step of fixing a base end of the pipe material to the hole at an open end of the hole;
and a filling step of filling the hole with a filler through a filling hose,
The pipe material has a communication hole that communicates between the inside and the outside,
The discharge port of the filling hose is disposed vertically below the communication hole,
In the filling step, the filler is filled between the outer circumferential surface of the pipe material and the inner wall surface of the hole from the opening end side, so that air in the hole is discharged to the outside through the communication hole.
Linear object installation method. A linear object installation method for installing a linear object in a hole formed in ground, comprising the steps of:
an insertion step of inserting a rod material having an expandable body at a tip portion thereof radially outward of the hole, the rod material having the linear body attached to an outer peripheral surface thereof along an axial direction, into the hole;
a tip portion fixing step of fixing the tip portion of the bar material to the hole by expanding the diameter expansion body radially outward;
a base end fixing step of fixing a base end of the bar to the hole at an open end of the hole;
and a filling step of filling the hole with a filler through a filling hose,
an exhaust pipe for exhausting air in the hole to the outside during the filling step is provided along the bar;
The discharge port of the filling hose is disposed vertically below the open end of the exhaust pipe,
In the filling step, the filler is filled between the outer circumferential surface of the bar and the inner wall surface of the hole from the opening end side, so that air in the hole is exhausted to the outside of the hole through the exhaust pipe.
Linear object installation method. A linear object installation method for installing a linear object in a hole formed in ground, comprising the steps of:
an insertion step of inserting a hollow pipe material into the hole, the hollow pipe material having a distal end provided with a diameter expandable body radially outward of the hole and the linear body attached to an outer peripheral surface of the hollow pipe material along an axial direction;
a tip portion fixing step of fixing the tip portion of the pipe material to the hole by expanding the diameter expansion body radially outward;
a base end fixing step of fixing a base end of the pipe material to the hole at an open end of the hole;
and a filling step of filling the hole with a filler through a filling hose,
an exhaust pipe for exhausting air in the hole to the outside during the filling step is provided along the pipe material;
The discharge port of the filling hose is disposed vertically below the open end of the exhaust pipe,
In the filling step, the filler is filled between the outer circumferential surface of the pipe material and the inner wall surface of the hole from the opening end side, so that the air in the hole is exhausted to the outside of the hole through the exhaust pipe.
Linear object installation method. In the base end fixing step, a sealant is injected between an outer circumferential surface of the pipe or the rod and an inner wall surface of the hole at an opening end of the hole.
The linear object installation method according to any one of claims 1 to 3.

Images